Here the town is an uncountable noun When referred to work place or place where I live and don’t use an article.But in the conversation if I had mentioned the word town or spoke about it already,should I have to say I am leaving town for a few days or I am leaving the town for a few days?
I am leaving town is an expression. It means that you are going away. The assumption is that you are leaving either the town where you live or the town where you are staying. But this is not explicit. We don't know what town it is. Adding for a few days makes the period clear. Without a time reference, the suggestion is that you are moving away.
I am leaving the town is something you would say after you or a third party had already mentioned the town concerned. The implication here is that you are moving away from the town you are speaking about and going to live somewhere else - although, again, this is not explicit.
Examples of the uses would be:
I am leaving town for a few days to go camping in the woods.
I am leaving the town (already mentioned) to look for work in the city.
The key difference is that the use of the definite article requires the town concerned to be specified.